In the field of refrigeration and air conditioning, 1,1,1,2-tetrafluoroethane (R134a) that is a hydrofluorocarbon (HFC) and R410A that is a mixed refrigerant of difluoromethane (R32) and pentafluoroethane (R125) in a mass ratio of 1/1 are currently widely used as refrigerants for a refrigerator, a vehicle air conditioner, a room air conditioner, industrial refrigerating machine, and the like.
Patent Literature 1 discloses, as a refrigerating machine oil for an R32 refrigerant, an ester synthesized from trimethylolpropane and/or neopentyl glycol and a specific dibasic acid, and a monohydric alcohol or a monocarboxylic fatty acid. Besides, Patent Literature 2 discloses, for use together with a single R32 refrigerant or a mixed refrigerant containing 50% by mass or more of R32, an ester-based refrigerating machine oil containing 20 to 60% by mass of a monobasic fatty acid having 5 or less carbon atoms, using a branched fatty acid as a fatty acid having 8 or more carbon atoms, and having a viscosity at 40° C. of 32 to 100 cst.
Furthermore, with respect to a base oil for a general industrial lubricating oil, Patent Literature 3 discloses a lubricating oil base oil consisting of a synthetic ester obtained by reacting an alcohol component containing 90% by mass or more of trimethylolpropane with a carboxylic acid component that contains a monocarboxylic fatty acid having 8 to 12 carbon atoms and adipic acid, and further contains, in a total amount of 90% by mass or more, caprylic acid and/or a monocarboxylic fatty acid having 8 to 12 carbon atoms containing 90% by mass or more of caprylic acid in total, and adipic acid.